1. Field of the Invention
This invention relates to an ocular pressure-reducing device employed in reducing lymph and/or fluids in the eyelid and orbit, which may have accumulated naturally or were injected during an anesthetic procedure.
2. Description of the Related Art
The eye is essentially a large sphere with a part of a smaller sphere incorporated in the anterior surface, constituting a structure with two radii of curvature (as shown in FIG. 1).
The orbit, which contains the eye, is a bony cavity in the skull housing the eyeball and its associated structures. Such an arrangement creates a cavity capable of containing fluids in or around the eye; this cavity is subdivided by the non-homogeneous structures therein. For example, one such cavity, known as the choroidal space, separates two of the three layers of the eyeball. This space, separating the sclera from the retina (as shown in FIG. 1), may, for example, become filled with blood or other fluids during a surgical procedure. Accumulation of excess fluid in this space can cause traction on the capillaries in the space to cause a sudden increase in intraocular pressure, which precludes further surgery in the eye and possible expulsive hemorrhage with damage to the retina and permanent visual loss. Most eye surgeons like to have the volume of the choroidal space reduced to minimum before "opening the eyeball" for cataract and other forms of eye surgery.
The eyeball is filled with fluids, namely, the aqueous fluid and the vitreous gel. The orbit is filled with muscles and fat, which contain fluids. The amount of this fluid varies considerably from orbit to orbit. The volume of fluid in the orbit is suddenly increased when local anesthetic solutions are injected into the fatty tissues around and behind the eyeball.
Before starting intraocular surgery, most surgeons would like to have a "soft eye" and minimal fluids pressure against the eyeball, as well as a low choroidal and vitreous volume.
Intraocular pressure-reducing devices are commonly used before eye surgery to reduce normal fluids in the eyeball and orbit, any excess fluids which are present in some persons, and fluids injected with anesthetic solutions.
Essentially, devices have been used to exert a pressure on the eyeball such that some of the fluid in the eye are forcibly ejected into the veins which drain the eye. Furthermore, these devices prevent further fluid accumulation by reducing arterial capillary blood flow. Previous devices of this type have utilized articles such as a container of mercury, rubber balls, inflatable balloons and sponges attached to an adjustable headband to apply pressure to the eye. Each of these devices have disadvantages, however. The mercury bag, for example, requires the patient to be immobile and be in the supine position for a predictable application of force.
Furthermore, these devices often lose their effectiveness as fluids exit the orbit thereby decreasing the amount of pressure exerted by the device on the arterial capillaries, allowing fluid to reaccumulate.
In addition, these articles may potentially inflict damage to the eye by directly applying pressure to the cornea and by applying an excessive pressure to the eye so to interfere with the metabolism of the retina and optic nerve. For example, U.S. Pat. No. 4,175,562 to Honan discloses a cup-shaped bellow which bears against the closed eyelid of a patient. The bellow is inflated to apply varying amounts of pressure on the eye. However, one of ordinary skill in the art will appreciate that such a device, in applying pressure directly to the cornea, has the potential for damaging the cornea. Furthermore, the use of this device does not assure a uniform and constant pressure distribution to the eye particularly after fluids have exited the eye thereby decreasing the applied pressure by the bellows on the eye. In spite of the adjustable pressure mechanism connected to the bellow, therefore, pressure application declines with fluid loss. Furthermore the device does not apply uniform pressure to the orbit; for example, it may produce no force on the orbital tissue of large orbits.
U.S. Pat. No. 4,303,063 to Stahl discloses an ocular massage device with an inflatable member placed between a rigid curved plate and a patient's eye. However, such a device shares similar disadvantages with the bellows disclosed above.
Other devices have alleviated some of the above-noted disadvantages while raising new difficulties. U.S. Pat. No. 3,952,735 to Wirshafter et al. appears to disclose an eye bandage for attachment to the area surrounding the eyelid of a patient with a pneumatic cushion composed of a closed cell or multi-cells which may be contoured to provide a desired pressure distribution on the eye of a patient. However, one of ordinary skill in the art will appreciate that such an eye bandage has the potential for creating corneal damage if an excessive pressure is applied to the eye by tightening the eye strap. Furthermore, fluid loss from the orbit will alter the amount of pressure exerted by the device on the eye, thereby hindering a uniform pressure application.
Another ocular pressure-reducing device, named the "Super Pinky," has also been used to reduce intraocular pressure. This device is essentially a hard rubber ball which is applied to the eye to reduce intraocular pressure; it also causes orbital fluid loss. However, such a device also applies potentially damaging pressure directly to the cornea while also potentially damaging the eye. The eye may be particularly damaged if the headstrap which applies the ball to the eye is excessively tightened or, if the eyeball is unable to retreat deep enough into the orbit. Furthermore, as the orbital fluid is resorbed, the device may come to rest on the bony orbit to cause pressure damage or allow fluids to reaccumulate in the eyeball.